An X-ray is an electromagnetic wave having a wavelength from about 0.01 to about 100 angstrom (Å) and can be used to obtain the internal structure of an object. Therefore, X-ray devices are widely used for photographing the inside of a living body or for common non-destructive industrial inspection.
The basic principle of a photographing device using X-rays is to transmit X-rays emitted by an X-ray tube (or an X-ray source) to a target object and detect a difference in the intensity of the transmitted X-rays via an X-ray detector and thus obtain the internal structure of the target object. When an X-ray apparatus includes a plurality of X-ray detectors, it is necessary for a user to check which of the X-ray detectors is mounted to a frame of the X-ray apparatus or a direction the corresponding X-ray detector is mounted to the frame of the X-ray apparatus.